(A,B) Basal currents were elicited with a voltage step from −40 mV to −120 mV for GIRK1+GIRK2 channels (Ba2+-sensitive, light blue), GIRK2 channels (Ba2+-sensitive, blue) and mutant GIRK1+GIRK2(L173R) (QX-314-sensitive, pink). The mean current (black line) is shown with ± SEM (N=9). Dashed line indicates zero current level. Note similarity in kinetics for GIRK1+GIRK2(L173R) and GIRK2 alone. (C) Plots show the response to bath application of PrOH (100 mM, orange bar), Baclofen (100 μM, red bar), QX-314 (100 μM, blue bar) and Ba2+ (1 mM, green bar) for HEK293T cells expressing the GIRK1-GIRK2 dimer and GIRK1-GIRK2(L173R) dimer. Note the mutant heterotetramers show no activation or inhibition. (D) Bar graph shows average basal current density (± SEM) for GIRK1-GIRK2 dimer (Ba2+-sensitive) and GIRK1-GIRK2(L173R) dimer (QX-314 sensitive).